Biodegradable polyester is a kind of macromolecule material using biological resources as raw materials. With respect to a petroleum-based polymer using petrochemical resources as raw materials, the biodegradable polyester can be degraded during a process of biological or biochemical effect or in a biological environment, being a very active degradable material in the present biodegradable plastic research and one of the best degradable materials in market application.
However, owing to effects of microorganism, illumination, radiation, atmosphere and contacted physical environment, a molding product prepared with the biodegradable polyester is relatively easy to age and degrade during storage and use, which hugely influences service performance of the product. A conventional method that solves the aging and the degradation of macromolecule material includes adding an antioxidant, a UV absorbent, a HALS stabilizer and the like into the material. For example, patent WO 2009/071475 discloses a mulching film of polyethylene which contains hydroxyphenyltriazines as the stabilizer. CN 103687902 introduces the UV absorbent and the HALS stabilizer, or a light stabilizer combining both, for providing the mulching film with UV stability. Although the above stabilizers can provide certain stabilization, they are definitely not satisfactory for a transparent mulching film, especially for that with a relatively low wall thickness.
Besides, under a condition that the molding product prepared with the biodegradable polyester composition is digested with 95% ethanol, there will be a precipitate separating out of a surface of a film or a part of the molding product, which thus influences a surface appearance property of the film or the part.
The present invention surprisingly finds by research that by adding a trace amount of a cyclic ester compound in the biodegradable polyester composition, an anti-oxidative property of the biodegradable polyester composition can be enormously enhanced, and meanwhile it can be guaranteed that the biodegradable polyester composition has an excellent surface appearance property.